1. Field of the Invention
The present invention relates to a disk array system including a plurality of disk drives that drive disk recording media, and more particularly, to a technique for cooling the disk drives.
2. Description of the Related Art
With advances in computer technology, high-density modularization and integration of electronic devices for computing systems are being carried out. For example, a compact disk array system including a plurality of disk drives that is highly modularized has been proposed as a recording medium for recording information necessary for a computer system. The highly-modularized disk drives each have a low-profile construction, including a magnetic or optical disk recording medium (recording disk), a disk unit including a read/write head for recording/reproducing information on/from the recording disk in a thin case, a controlling circuit for controlling the disk and the head in the disk unit, a control board including a controlling circuit for controlling the recording disk and the head in the disk unit, and a connector for connecting the control board to an external controlling device. The thin case for the disk unit accommodates a driving motor for rotating the recording disk and a driving mechanism including an actuator for controlling the recording medium.
With the disk array system, for the purpose of improving reliability of data storage of the recording disk, the disk drives are accommodated in a plurality of unit boxes stacked one on another and two columns of the tiered unit boxes are disposed back-to-back. This type of large disk array system is applied to a high-capacity storage device. The disk array system can be used for a redundant array of independent disks (RAID), or by connecting disk drives via a high-speed special-purpose network such as an optical network and controlling the drives with software, the disk array system can be used for a storage device in a storage area network (SAN) or in a software redundant array of independent disk (NAS).
When densely-integrated disk drives are aligned and accommodated in a unit box, heat from the disk drives raises the temperature of the unit box, resulting in malfunction in devices constituting the disk drives. Electronic devices generating heat in the disk drive are a driving motor, an actuator, and an LSI constituting a controlling circuit. To address this problem, cooling the disk drives is essential.
In a known disk array system, a cooling fan for blowing cooling air over the vicinities of the heating disk drives is disposed in a casing where the heating disks are accommodated. If cooling is not well performed, the temperatures of the disk drives increase or differ from disk drive to disk drive, resulting in operational malfunction or low long-term reliability of the disk array system.
To address the aforementioned problem, a technique to provide a heat-dissipation mechanism, such as fins, in a disk unit has been proposed. With this technique, cooling air can readily pass through a large heat dissipation area, thereby improving cooling performance (see Japanese Unexamined Patent Application Publication Nos. 2000-156077, 2001-332978, and 2003-347781).
Furthermore, with the disk array systems, even higher-capacity recording disks and higher-density disk drives are demanded.
However, when the aforementioned heat dissipation mechanism such as fins is disposed in the disk unit, one disk drive takes up a lot of space in the unit box, resulting in decreased density of the disk drives in the unit box. Because of this, the fin cannot be made large, whereby cooling performance is degraded.
When the disk drives are densely integrated without providing the fins in the disk unit and heat is dissipated from the surface of the disk unit itself, cooling air passes through extremely slim gaps, e.g. several millimeters, between the disk drives. In this case, since the cooling performance is greatly influenced by the deviation of the installation positions of the disk drives, the temperature increase of the disk drives differs depending on the position. Due to this variation in temperature increase, the temperatures of some disk drives may exceed the tolerance temperature. To prevent this problem, the gaps between the disk drives need to be made larger, which conflicts with the high-density packaging requirement.